To all doubters: my splitter/combiner ist a standard circuit, many solutionss can be found on the web. From .3 to 30 MHz both output ports exhibit the same signal amplitude when each port is terminated with 50 Ohms. The difference in receiving performance is definitely that my R-390A is inferior to my 51S-1 which it should not be. I use the symmetric antenna input of the R-390A with a balun that transforms 120 Ohms symmetric to 50 Ohms unsymmetric. -Karsten-
-----Ursprüngliche Nachricht----- Von: Bob Camp [mailto:kb...@n1k.org] Gesendet: Freitag, 7. Februar 2025 23:53 An: Karsten Simon Cc: R-390@mailman.qth.net Betreff: Re: [R-390] R-390A help needed Hi Ok, this gets a bit crazy ….. A normal 3 db splitter *assumes* that it has 50 ohm loads on both outputs and a 50 ohm source. A typical receiving antenna is likely not a 50 ohm source. These radios do not provide 50 ohm loads. The net result may be a splitter that is very confused about what it should do. Quick and a bit stupid solution: Put 6 db pads on the input and both outputs. Now they all are much closer to 50 ohms. The splitter should be much more happy. No you don’t want to run things this way forever and ever. It’s just something to do to rule out the splitter as part of the problem. Would I bet anything on this being the issue? Nope. However it’s still worth checking. Bob > On Feb 7, 2025, at 5:38 PM, Karsten Simon via R-390 <r-390@mailman.qth.net> > wrote: > >> Try swapping the receiver connections at the switch and check again > That was the first thing I had done of course > > -----Ursprüngliche Nachricht----- > Von: r-390-boun...@mailman.qth.net [mailto:r-390-boun...@mailman.qth.net] Im > Auftrag von William Blodgett via R-390 > Gesendet: Freitag, 7. Februar 2025 23:34 > An: R-390@mailman.qth.net > Betreff: Re: [R-390] R-390A help needed > > First, verify the route through the switch is “equal” to both receivers. Try > swapping the receiver connections at the switch and check again > > P.S.- Both are great radios ! > > 73, > Bill > AI5RP > ++++++++++++++++ > Bill Blodgett > Arlington, Texas > USA > >> On Feb 7, 2025, at 12:22 PM, Karsten Simon via R-390 <r-390@mailman.qth.net> >> wrote: >> >> >>> >>> are you using the same antenna for both radios? >> >> Yes. Both are connected to the antenna selector switch via a two port -3db >> splitter. >> >> ______________________________________________________________ >> R-390 mailing list >> Home: http://mailman.qth.net/mailman/listinfo/r-390 >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:R-390@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ > R-390 mailing list > Home: http://mailman.qth.net/mailman/listinfo/r-390 > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:R-390@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > ______________________________________________________________ > R-390 mailing list > Home: http://mailman.qth.net/mailman/listinfo/r-390 > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:R-390@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:R-390@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
